Was starting fine until I was working on the exhaust manifolds .

Too large a voltage drop during starter and engine rotation ( starter sag )

Initial fuel pump turns on to charge the fuel rail with pressure ( gauged )

9.0 volts on the instrument cluster and on the right fuse box terminal post with a separate meter

Not enough voltage to properly power the engine ECU , no injector pulse

Starter will rotate the engine just fine

By lifting the starter cable from the terminal post on the right engine compartment wheel well ( point ST3 on the wiring diagram above ) , no starter sag and voltage stays high enough to power the ECU but without starter rotation but starter solenoid clicks strongly

This is one that has stumped me when I got sick with final stage kidney ( s ) failure

Some things I have done :

New battery and tested old one with a large load tester ( good ) , fully charged

Battery terminals snug and used battery shim on positive battery post

Battery ground cable good

Positive battery terminal large Megafuses not blown and terminal nuts tight

Replaced starter 4 times with new starter solenoid at least 5 times for this issue

Editing while I do Kidney Dialysis


Something I tried was to run the starter with one separate battery and the rest of the car including the engine ECU with the normal Battery location

had the starter cable terminal connection separated at the right wheel well and powered by the 2nd battery alone . Removed fuse # 10 right engine bay fuse box ( alternator voltage excitaion )

This so I can reconnect to original battery cable configuration after the engine start and then reinstall the alternator fuse

No help and same starter sag 9.0 volts

The problem I am seeing and can't get past is the output terminal post of the starter solenoid has a case ground path of 1 ohm and 2 ohms for a Bosch manufactured and stamped solenoid ; this while the pigtail wire is lifted and isolated on a test bench

This drains the battery amperage / voltage relationship capacity in a dynamic since as a current dependent circuit

Large engine / starter ground strap cleaned and tightened ; but the problem as I understand it is an excessive current is going down the ground path and not the pigtail that makes the starter spin . I know it spins the engine enough by the tach at 300 RPM but too much other current shorts from that solenoid output post through to car frame . I know about engineering compromises to make a circuit work but the short is too much of a percentage lost and drawing the whole car down in voltage




These are pictures from al_roethlisberger Veteran Member

Watt700 in Australia had a problem in this triangle covered terminal / fuse point ST7 on the wiring diagram above

Notice if you have not been there the black triangle under the black / white stripped wire bundle , this is under the right rear seat pan behind the right heelboard

 

firewall grounds?

megafuses loose?

 

Thanks , I will check the grounds in the morning

Megafuses not blown and terminal nuts removed and retightened ; but did not check the terminal nuts under the rear seat pan ( black plastic triangle cover )

I didn't want to put 2 batteries in parallel in the trunk to avoid having too mush current running through the Megafuses or the rest of the battery cables through the car up to the starter problem area

Battery ground good


I did remove some grounds from the right forward chassis rail by the right headlight area

Im scared of the dark

 

Edited both above post for better clarity and dialysis done for tonight

 

I think your idea of running the starter from a separate battery is a good diagnostic step, but I would try and isolate the starter completely.

So in your diagram above, disconnect the Alternator from the starter, and also unplug the starter relay. Manually trigger the starter solenoid from that relay socket with a small jumper wire and a momentary switch from the 2nd battery.

If you still get the voltage sag on main battery in this set-up then you have established it's not the starter that's causing it.

 

If I'm reading this correctly, I think that could be normal. I have a spare starter in the garage. I just put some leads on it to test for you for comparison. 0.6 ohms with pigtail connected, 1.6 ohms on post with pig tail disconnected. This starter came from a running car - i removed it myself.

Hope this helps.

 

Thanks Brendan ,

The meter test you show is exactly what I am seeing in the first picture as I have 4 X300 starter / solenoid assemblies on the garage floor

on disassembling the starter motor and spinning it up on the engine I see nothing wrong with the starter motor

Tried earlier with a starter / solenoid assembly from a donor car at the local salvage yard , no help but there was the chance that that starter was bad

Just woke up and haven't stirred up awake yet , haven't had my tea yet

in cleaning up my jumper cable connections with the 2nd battery last night the voltage sag was better and just barely below the red band on the instrument gauge

The neighborhood homeowners association is putting heat on me to at least get it in the garage , and I don't understand , It's the prettiest Jaguar on the whole block

Once I get it started and relax the starter relay the battery voltage should return to normal .........in theory

The latest starter / solenoid assembly tried was a Bosch labeled and stamped remanufactured unit fresh out of the box

The solenoid is stamped as a Bosch and would expect that to be a new manufacture

I will try your suggestion in your post # 5

Thanks , Joe Barry

 

Batteries recharged but have alarm going off , maybe out of sequence

Cycled key no help , so will be trying FOB after finding FOB batteries for both fOBs

Still same 2 battery configuration as tried last night in the 2nd wiring diagram drawn but will try some starter fluid aft of the MAF before trying Brenden;s suggestion

18-09 Keyfob Transmitter Battery Replacement.pdf (jagrepair.com)

two CR2016 batteries

Barely had enough voltage during starter sag last night so it was an improvement

 

Cant help with the electrics, but you say the problem began when you worked on the exhaust.
Did this involve a very short trip to inside the garage?
Is there any chance you may have bore wash? Maybe worth checking compression and if low then adding a spoonful of oil onto the pistons.

Peter

 

Good point and will put a bit of oil on the top of the cylinders and turn it through a couple of rotations

I got stuck on the starter solenoid output post an almost direct shorting to ground so tried other starter solenoids but Brenden showed I was not unique and was seeing something that I thought was obviously wrong on mine , A second mind helps .

That could be my problem all along as the dried up oil on the cylinder walls my be not allowing the engine / starter to rotate more freely dragging down the voltage '

This would be a modified version of bore wash

The starter sag voltage is getting better before your suggestion and almost in range so the ECU is at least powering up somewhat giving me RPM indication I lost before with at least the 1st power from the RH engine bay relay ( ignition positive relay )

RPM is more like 200 then the 300 normal

The RH engine fuse box relay clicks as you remove and reinstall it with the key in the run position and the ECU controlled relay bench test OK and is needed to power the injectors but I'm running a one person operation

So I,m working with what I got ..........and that's not alot

I will drain and refresh the fuel as well as it is suspect , I drained and refreshed it before the Covid outbreak , but that was some time ago hence a new battery as it is probably 4 years old as I load tested the 1st battery back then

The fuel cap was bubbling air as the clogged fuel filling well was topped with water as the water drain line was clogged

Bubbling air out so it was probably drawing in water to the tank fuel as the temperature changed in the other direction

It's been sitting a couple of years during my medical journey but had long engine runs in the driveway if my memory is correct

Kidney failure effects your brain function as unfiltered and dirty blood sluggishess up the brain , my kidney ( little Bubba and little BoBo ) function is at 3 % but an excellent body through the many test to except a transplant through the Kansas University Kidney Transplant program

As long as I get a couple of cylinders to kick over , this may help the voltage recover to bring in the injector pulsing and a shot of starter fluid aft of the MAF may aid that along and recover a battery voltage and then fuel from the normal source

Maybe after a run in I will be able to return to single battery starting operation

I will put a bit of penetrating oil on the top of the cylinders and let it soak and a lot of smoke in her coming alive revel announcement to my neighbors

 

Parker 7 - sending good thoughts and wishes your way for car and kidney! Hard to believe folks want your Jag in a garage vs public display.

 

They didn't bother to ask how I'm doing and ask is there anything we can do to help

One time I asked Penelope is she's a pretty girl

And she replied back "I'm a VERY pretty girl "

So I'm sure the neighbors are tired of hearing her say that in the days after that

Women get like that , just saying

But the neighborhood association has sict the city with a written city code violation letter with a couple of days left before removal

Lab test excellent with the Doctors visit today

Gotta clean up the leaking battery corrosion in one of the FOBs to reset the alarm as the blasting horn is very effective so I will probably remove the horn fuse being the SLCU needs to be powered for the starter to enable

 

Neighbors and city jealous of Penelope, that is obvious

Excellent labs - excellent!

Have woken up my teenager from across the compound here due to faulty FOB - definitely gets the heart rate going until the car battery can be disconnected

Cheers

Cafe

 

There is a fuse # 4 or 5 in the trunk that you can tie a string around to be able to yank out faster

Which reminds me a hard reset may get my security system back in sequence

 

Hi Parker,

I'm just now reading your thread, and the first question that comes to mind is: "What were you doing around the exhaust manifolds and what other wires, connectors, hoses, or components might have been disturbed?"

Have you scanned it for any stored diagnostic trouble codes?

I'll be praying that a kidney becomes available soon, that your homeowners association will give you some grace (give people a little power and they become despots), and I hope you will not push yourself too hard in the meantime.

Blessings,

Don

 

Changing cracked manifold

May have been enough time ( years ) to set up dragging cylinder walls if that is possible and Cafcpete Senior Member clued me into that assumption and is still an assumption and the aids I will give it to proceed along

That's why it still has 110 K miles', I drove before

Starter solenoid relay connector secured

Starter cable and terminal post ( post tight on wheel well so the connection underneath the wheel well should be tight ) on right side secured

under car the starter solenoid heavy battery cables in correct position and tight ( assembled battery cables and small solenoid control wire on solenoid outside the car before starter installation up into car

I need to remove the B + alternator post connection and insert the wire terminal into a leather glove

Running a long hard reset and then will try removing the horn fuse if the alarm still sounds off

Fob with new batteries does not light when depressed but the Fob is inside out of range

Fob worked before but then could be not the case of the light going given inside the house

The alarm stopped the starter enable ( just recently with the alarm sounding and recently I had starrer / motor rotation so I need to get past that alarm before resuming starter troubleshooting again

Almost had enough voltage during starter sag but that in later tries the alarm came into issue

Lubed the cylinder walls and has soaked

Not able to read codes at this time but I can download new software to get a ELM327 reader working in my hand

I need to check the crash switch jumper is still jumperd

"homeowners association will give you some grace (give people a little power and they become despots) "

Especially that no one bothered to ask

I've got a single word definition for that , the word starts with the same D letter , but the children keep me silent

 

Alarm back to normal off and starter rotates the engine

Hard reset was all I did for the alarm

On to starter / engine starting up problem

 

I seem to recall that part of the fuel pump relay circuit passes through your favorite electrical connector, Papa Indy 61 (PI61), located behind the right headlamp, not far from the forward exhaust manifold. Any chance that connector was disturbed?

Cheers,

Don

 

Got my starter / engine rotation back

Yea that was a weird wire routing back forward

Will put a heavy jumper wire in the fuel pump relay socket to power the pump at all times

The same wire is used from the ECU to the relay control half for both the initial 4 second fuel rail charge ( or prime )

I do hear the fuel pump for the initial fuel charge

I need to check the crash switch jumper wire and hook up the 2nd battery to get it over the hump

 

Update

With the single fully charged factory battery configuration . Starter / engine rotation but low RPMs ( 150 ) but have instrument indication , large starter sag 9 volts , starter fluid no help or a singe cylinder firing off

With 2 fully charged battery configuration with the second battery only tapped into the starter cable as in the first picture very very weak starter rotation but voltage gauge stays high maybe 12.75 volts

Used starter fluid and no light off

Suspect poor heavy gauge jumper cable connection with the 2nd battery as I had better results with this configuration the day before

So with 2 battery configuration : good voltage on the gauge ( 12.75 )during starter rotation so ECU should be fully powered but very very low starter speed , should be getting injectors pulsing

With single battery configuration large starter voltage sag ( 9 ) but 150 RPM starter speed

Still need the check the battery cable connection under the rear seat pan and isolate the B + alternator post wire and fuel pump relay jumper